Also add the option to name columns in the cooling i/o

src/cooling/Compton/cooling_io.h

src/cooling/EAGLE/cooling_io.h

src/cooling/QLA/cooling_io.h

src/cooling/const_du/cooling_io.h

src/cooling/const_lambda/cooling_io.h

src/cooling/grackle/cooling_io.h

src/cooling/none/cooling_io.h

src/parallel_io.c

src/serial_io.c

src/single_io.c